If you're a Linux or Windows convert, and you have a big library of either .DV files (Kino in Linux) or .AVI files (i.e. DV-AVI files, not to be confused with regular .AVI movies), I've found a much faster way to import them into iMovie. (There is a previous hint about this, but it appears to work for an older version of iMovie. The following is for using with iMovie 09+.)

First, make sure that you have the right kind of files. If you were using Kino in Linux (or perhaps some other video editing tool in MacOS), you have files with a .dv extension. Those are "raw" DV files and will work fine.

DV-AVI files also work and do not require conversion. These are not Windows AVI movies. These are actually DV files with an AVI wrapper around them. You would probably only have these if you imported video in Windows using something like Pinnacle Studio (what I was using prior to converting to Mac). Kino in Linux can also make DV-AVI files instead of its default .DV files. It's also possible that this will work only with Type 1 DV-AVI files; Type 2 files, where the audio file is in a separate file, may not work.

OK, so you have a bunch of directories with DV or DV-AVI files to import. Each directory that you're going to import is going to become an event, so make sure they're organized the way you want them to be organized.

Then, for each directory containing files you want to import into iMovie, do the following:

Move the directory into the iMovie Events directory in your Movies folder.

Create the following subdirectories within the moved directory: iMovie Cache, iMovie Thumbnails, and then iMovie Cache within the iMovie Thumbnails directory. You can do this by creating a directory with those subdirectories in the Finder, use Edit » Copy to copy those directories once, then use Edit » Paste Items to paste them into each directory you want to import.

(The -p tells the second command to make any parent directories it needs to, so it makes the iMovie Thumbnails directory first, then creates the iMovie Cache directory.)

Do these two steps over and over until you've done this for all directories you want to import, then just start iMovie. It will automatically notice the new directory, create the cache, playlist, and thumbnails for your movie. The more directories you do this with, the longer iMovie will take to create everything, of course.

[robg adds: If you have a ton of these to do, you could, in theory, create the above shell commands as a new Automator Service, and then just select each folder to be modified in the Finder and activate the Service. I haven't actually tested that, but it should work.]

Are you sure this doesn't work by doing *only* step 1? I've been running an import script with my digital camera for over a year that just creates a folder in the iMovie Events folder then moves the imported .AVIs into the newly created event folder.